This invention relates to a rotary vane device and more particularly but not exclusively, to a rotary vane engine or pump. The invention also relates to a rotor assembly suitable for use in such a rotary vane device.
Rotary engines and pumps are well known in the art. One common embodiment of this technology utilizes a rotor having a plurality of vanes extending radially outwardly therefrom, with the vanes being radially displaceable relative to the rotor. More particularly, the vanes on a rotary vane device travel in and out of the rotor as they move along the interior walls of the housing of the rotor. Centrifugal force or springs are used to urge the vanes towards or against the outer wall. In their extended state, these vanes adjust to the housing's (or cylinder's) profile while being driven by the rotor. The displaceable vanes, used in combination with a rotor mounted offset relative to a cylindrical housing in which it is located, result in the formation of varying volume chambers between the rotor and the housing, with the volume of a chamber changing as the rotor rotates inside the housing.
Common uses for a rotary vane pump include hydraulic fluid compression and compressed air pumps, for example in aircraft or trucks. Small rotary vane pumps can also be used for drink dispensers, medical dispensing pumps, water pumps on marine engines, compressed air drills and many other applications. The materials used to make the pump and vanes can be modified for high-temperature industrial applications such as furnace air injection or engine turbocharging. Rotary vane pumps also work well as vacuum pumps for example in aircraft applications, laboratory vacuum systems, medical applications and also to evacuate and recover refrigerants from air conditioning systems. Rotary vane engines are also known in the art.
A good seal is required between the end of a displaceable vane and the housing surface in order to maintain the efficiency of the rotary vane device. Centrifugal forces exerted on the vanes inherently contribute to ensure that a good and dynamic seal is formed between the end of a vane and an inner surface of a rotor housing. However, in some cases centrifugal forces are not sufficient, and it has accordingly been proposed to use springs to augment the outwardly directed bias of the rotating vanes. Springs, however, wear over time which adversely affects the performance and reliability of a rotary vane device incorporating spring driven vanes. In addition, it also complicates the maintenance of the device.
It has been proposed to use magnets instead of springs to provide the required bias. Although this works well, some shortcomings are associated with this solution in certain applications. For example, there is limited space to mount magnets in both the vanes of the rotor and the rotor body, and the maximum magnetic flux that can be obtained is therefore limited by the size and number of magnets that can be used due to geometrical constraints. One way of overcoming this disadvantage is presented in the applicant's co-pending application ZA2014/03295 entitled “Rotary Vane Device”, the contents of which is incorporated herein by reference. In this embodiment, rotor magnets are located in the body of the rotor adjacent the vanes, and not operatively below the vane slots as is known in prior art applications.
A further disadvantage associated with existing magnet based solutions is that the vanes also have to be reasonably thick to accommodate a suitably sized magnet, and therefore take up valuable chamber volume in the process.
Existing rotors are furthermore mostly made from ferromagnetic materials, which interfere with the magnetic flux generated by the magnets, and therefore impede the efficiency of the magnetic bias.
It is accordingly an object of the invention to provide a rotary device that will, at least partially, alleviate the above disadvantages.
It is also an object of the invention to provide a rotary device which will be a useful alternative to existing rotary devices.
It is a still further object of the invention to provide a rotor for used in a rotary device that will, at least partially, alleviate the above disadvantages.
It is another object of the invention to provide a rotor for a rotary device which will be a useful alternative to existing rotors.